all new brake parts, still sticking 75 chevy truck?
its had a new booster, master cylinder, suitableness valve, calipers twice because we thought we got bad ones the first time, new rubber lines accepted to calipers, pads, and rotors turned. every day the pedal is different, sometimes its soft, and have laudatory brake response then others within like an inch the pedal is hard and have to push penetrating to get brakes, its hot out now, almost 90 and the brakes start sticking when it gets this way, at night they as usual dont stick, I did try to take fluid out of the master cylinder and didnt help.
I own a purchase, and I think something is missing here. What kind of vacuum do you have on the engine? Does this engine have a ripe lift cam in it? Everything you are saying leads me to believe you don't have the vacuum you should have, or you have a bad booster. Another thing that can provoke your problem is the wrong brake fluid. When brakes get hot, sometimes they will boil the fluid in the annulus cylinder causing air bubbles to form inside the caliper. Try going to a DOT-4 fluid if you have to. You must have at least DOT-3 in it now, any less and you will have these problems. DOT-4 has a very extreme boiling point, where as DOT-3 has a lower boiling point, and so on. If you put bargain brand protean in it, and the brakes get hot from using them a lot (like coming off a mountain) the fluid will boil, and you will cool off brake pedal. Combine this with low engine vacuum, and you will have all kinds of problems. In the furnish line (for the brake booster) you must have a check valve that lets air flow one way, but not the other. Tally to see if this valve is working, and that your booster is holding vacuum. Turn the vehicle off, hang about and hour or so, and remove the line at the booster. Did you hear a gushing noise as it equaled the HZ on the up? Since vacuum is air pressure in reverse, you should have heard the booster fill with air to equal it out. If brakes get hot, and start sticking, this is caused by a build-up of air bubbles in the caliper/on the short list for, and its just like putting the brakes on. Since they don't stick at night, then you have answered your own suspect. You must get good fluid, and bleed each wheel until you have all the old fluid out of the system. Start with the wheel that's farthest from the master cylinder, and m your way to the one that is the closest to the master cylinder. Your rear brakes aren't bad to do this, so at least get it all out of the front calipers if you can. This will take a lot of fluid to do it with, but I'm sure this is your incorrigible. If you watch NASCAR, you will see this happen to them on short tracks where they are using their brakes a lot. So... if you have vacuum as you should have, a fitting directional valve in the feed line to the booster, and the booster is holding vacuum, then this leaves only one fixation, and that's the fluid since you covered everthing else. It may be possible you have the wrong booster, bent rod, or rust in the lines, but I would remember this would make a constant problem, and not a problem that shows up when the brakes get hot.
Glad to support out, Good Luck!!!
